Recently, an organic solar cell using organic-inorganic hybrid materials such as organometallic halide as photoactive materials has received attention. In 2013, Professor Grachel's team (Switzerland) announced a solar cell having the same structure as a solid-state dye-sensitized solar cell but replacing existing organic dye only with an organometallic perovskite compound (CH3NH3PbI3) [Nature, 499, 316 (2013)]. Further, Professor Snaith (Oxford University, England) found that when some of iodine (I) is replaced with chlorine (Cl) in the same organometallic perovskite compound (CH3NH3PbI3), mobility of charges largely increased [Science, 342, 341 (2013)]. Accordingly, it was found that a cell having a similar structure to a multi-layer organic thin-film solar cell could be manufactured by replacing a porous TiO2 film which is an essential electron transport layer of the solid-state dye-sensitized solar cell with an Al2O3 scaffolder layer [Science, 338, 643 (2012)] or by removing the porous TiO2 film [Nature, 501, 395 (2013), Energy & Environ. Sci., DOI:10.1039/C3EE43161D (2013)].
From these recent results, the organometallic perovskite compound is possible to manufacture a simple thin-film structured device similar to other inorganic thin film solar cell, while simultaneously maintaining advantages of a low-temperature wet manufacturing process of the existing solid-state dye-sensitized solar cells or the existing organic thin-film solar cells.
However, the organometallic perovskite compound is based on a halogen element unlike other common oxide perovskite compound, such that it is difficult to completely remove instability of the metal halide itself according to hygroscopic property.
In addition, currently, the organometallic perovskite compound has a methyl ammonium (CH3NH3+) organic ligand having the smallest molecular size and having an iodine (I) group having the largest atomic radius as main components, and even though the organometallic perovskite compound has a three-dimensional cubic perovskite structure, a light absorption range is the maximum of 800 nm, which is narrow, such that it is not possible to be changed into a molecular structure where a wider wavelength is absorbed.